Hydraulic ship propulsion apparatus



Jan. 10, 1956 c. F. PIPER 2,730,065

mmmwuc SHIP PROPULSION APPARATUS Filed Aug. 30, 1954 mmvrox C'HKL F PIPER Un fi e s- P r O HYDRAULIC SHIP PROPULSION APPARATUS Carl F. Piper, Oakland, Calif.

Application August 30, 1954, Serial No. 453,173

1 Claim. (Cl. 115-14) (Granted under Title 35, U. S. Code (1952), see. 266) The invention .described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to propulsion systems and, more particularly, to methods and apparatus for propelling or advancing water-borne ships or vessels by a forceful discharge of admitted water.

As is well known, practically all vessels are propellerdriven, although sporadic attempts have been made to hydraulically propel the ships by taking in sea-water and forcefully pumping it through a stern tube. Some of these proposed drives have utilized a jet principle in which sea-water is ejected at very high pressures, but the efiiciency of such arrangements has proven at best questionable because the high pressure jet succeeds principally in drilling a hole in the sea wall. Other hydraulic drives avoid the jet difficulty by utilizing a volume displacement principle in which large amounts of sea-water are taken-in and expelled aft at a relatively low-pressure, the advance of the ship being achieved by physically moving or pumping a volume of water from the front to the rear of the ship and, of course, the rate of advance is largely controlled by the rate at which this large volume is pumped. In theory, at least, such a displacement principle is operative since the ship must move ahead to provide space for the discharged water, but, unfortunately, the practical difficulties encountered in employing the principle appear to be insurmountable. The principal obstacle, as might be anticipated, lies in the tremendous pump capacity that is required to pump the large volumes at a rate sufiicient to provide the desired speeds, and, without considering such capacities in figures, this fact, combined with conjunctive space requirements, have been dissuasive. Obviously, were it not for such deterrents, hydraulic propulsion might well have replaced the cumbersome, noisy, relatively ineflicient and expensive propellers with their long propeller shafts, shaft alleys, reduction gears and other mechanical appurtenances that require costly repair and are easily susceptible to battle damage or sea-water fouling. The situation then appears to be one in which the advantages of hydraulic propulsion long have been recognized, but thought and experimentation have failed to provide a practical solution.

Accordingly, a general object of this present invention is to provide a practical, efficiently-operating and eilective hydraulic propulsion and, more-specifically, the invention is concerned with accomplishing ship propulsion by so employing the described water-displacement principle as to bring the requisite pump capacity within practical limits.

Broadly analyzed, the invention is predicated upon the idea of expelling tr e requisite fluid volume by forcefully pumping only a limited fraction of that volume and by using the forced flow of this fraction to draw in such additional amounts as are necessary to constitute the total required for the desired displacement advance, The

ICE

principle employed for drawing this additional amount is that of a reduced pressure achieved by a somewhat conventional venturi tube arrangement, the forced fraction being moved through a constricted conduit section which forms a venturi neck and then being permitted to expand in an outwardly-diverging discharge conduit With the necessary reduced pressure so established, the constricted section of the conduit is communicated with the surrounding fluid, or sea-wall, which then is drawn in through the neck to be discharged aft through the diverging discharge tube.

With such an arrangement it will be appreciated that the pump capacity can be reduced materially over that which otherwise would be required to move the entire volume through the ship, and, in fact, the capacity need only be such as is adequate for establishing the requisite low pressure in the venturi. Although experimentation on large vessels has been prohibitive, such tests as have been made indicate that the pump capacity need be only that required for about 46% of the total volume, the remaining 60% of the volume being drawn in and expelled by the reduced venturi tube pressure. Further, it will be apparent that the venturi discharge tube can be regulated in length and divergency angle to assure that the'water expelled is at its most effective pressure which, obviously, will be below such pressures as have the undesirable characteristic of drilling holes in the sea-wall. The invention also contemplates utilizing the hydraulic system for braking, maneuvering and backing the ship, although these refinements will be considered in detail later. Also, as will become apparent, the scope of the invention contemplates the method as well as the particular apparatus now employed to accomplish the desired purpose.

The invention is illustrated in the accompanying drawings of which Fig. l is a schematic plan view showing a suitable hydraulic circuit arranged on a ship; Fig. 2 another schematic showing the same circuit elements in elevation, and Fig. 3 an enlarged elevation of such components of the hydraulic circuit as are used to create the hydraulic propulsion force.

Referring to the drawings, the components of the present invention are illustrated as being incorporated in a ship which, so far as regards the scope of the invention, may be of any size or type and, in addition, may utilize any conventional source of power, such as steam, diesel, electric, etc. As shown, the power supply of the illustrated ship is derived from a bank of boilers 2 adapted to feed steam turbines 3 which, in turn, drive centrifugal pumps 4, the force of each of these pumps being used to expel sea-water rearwardly through separate discharge conduits generally indicated by numerals 6 and 7. In addition, the intake water for pumps 4 is delivered through another pair of intake conduits 8 and 9, although, as has been indicated, the amount of water drawn in through this pair of intake conduits forms only a fraction of the total volume expelled through discharge conduits 6 and 7.

It also is to be noted that these various elements are shown in a schematic arrangement which, obviously would have to be disposed and proportioned according to the particular type and size of the vessel involved. Also, such adaptations would have to include computations and tests for determining the most eflective conduit sizes and dispositions, as well as the requisite pump capacities necessary for accomplishing the purposes to be described. No present attempt to specifiy such pump capacities or other structural details would be beneficial because, not only will the details vary with the different ships, but details for each ship will depend upon considerable empirical experimentation carried out under actual seagoing conditions. However, as will become apparent, the

pump capacity of the present hydraulic circuit is materially less than otherwise would be required to pump such a total volume as is necessary to produce effective, hydraulically-propelled advance of the vessel.

One of the primary features of the present invention resides in the use of the venturi principle to draw in a substantial portion of the sea-water necessary for the volume-displacement propulsion. Thus, instead of requring such a pump capacity as would be necessary to move the entire requisite volume, the present invention contemplates relieving the pumps of a substantial portion of this volume by utilizing the reduced pressure produced by a venturi constriction to effect the supplemental intake.

As shown in the drawings, such a supplemental intake is achieved essentially by forming discharge conduits 6 and 7 as venturi tubes, or, as shown, by forming these two discharge conduits with constricted venturi neck por tions 11 (Fig. 3) and outwardly diverging conduit walls 12. Forwardly of constricted neck portion 11 each discharge conduit is expanded to form a chamber 13 into which Water drawn in through pump intake conduits 8 and 9 is delivered by means of a nozzle 14. Further, in take of the supplemental quantity is permitted by providing additional intake conduits 16 and 17 for communicaring chamber 13 with the seawall surrounding the ships hull, conduit 16 being directed vertically downward and conduit 17 being projected at a suitable downward inclination in a forward direction. Also, for purposes to be described, nozzle 14 is so mounted as to be movable to either one of the dotted line positions shown in Fig. 3

and, of course, in these adjusted positions, the force of the nozzle jet is capable of expelling the water either directly downwardly or forwardly. Finally, to avoid damage to the internal mechanisms or surfaces, it is most desirable to mount wire mesh screens 18 on the mouths of each of the conduits to filter out foreign objects.

With such an arrangement, it will be apparent that,

when the pump pressure is sufficient to drive or impel the jet of water from each nozzle 14 through its constricted venturi neck 11, a reduced pressure is created in the outward divergence of discharge conduit 12 which, in

a manner common to venturi tubes, permits the water pressure in the discharge conduit to gradually reduce, this reduction of pressure in fact being the phenomenon which also creates the pressure differential necessary for drawing in the supplemental water supply. However, the reduced pressure of the water in the discharge conduit is a distinct benefit to hydraulic propulsion because it allows a low pressure discharge such as avoids the ineffective drilling phenomenon noted in the high pressure, low volume jet discharges. In the present arrangement, the ships advance is accomplished by discharging a large volume of Water at relatively low pressure and it is this fact which provides the efliciency of the drive that is so essential in bringing the operations within practical limits.

As also will be appreciated, the efficiency of the apparatus to a large extent depends upon the efficiency of the venturi and, for this reason, it will be come important to determine the most effective venturi neck diameter, as well as the converging and diverging slopes of the neck and discharge tubes respectively. The general considerations governing these slopes or inclines may be found in many source references, but, for present purposes, it is anticipated that the particular shapes will have to be established, principally through experimentation or through mathematical calculations as applied to presently detailed specifications relating to size, requirements, materials, temperatures, etc. Obviously, no present attempt to specifiy these dimensions would serve any useful purpose. Generally, however, it has been found that a venturi which has a conventional angle of divergence of about 20 and a downward stream cone with an angle of divergence of about 6 is capable of drawing in a suflicient supplemental quantity of water for advancing a smaller craft, although this recitation is not intended to limit the invention in any manner.

As may be noted, the illustrated hydraulic circuit includes two intakes 16 and 17, as well as a nozzle 14 that is so adjustable as to direct the pump flow into one or the other of these conduits. The purpose of such an arrangement is to adapt the hydraulic circuit for maneuvering the ship and such maneuvering may include either turning, stopping or reversing. To permit such maneuvering, it is desirable to mount such suitable batfies 19 in each of these conduits as will allow a selective use of one or more of them. Thus, if it is desired to reverse the ship, the flow through conduits 6, 7 and 16 can be shut-off and the flow through nozzle 14 directed forwardly through conduit 17. Similarly, a braking power can be applied to the ship by closing-off conduits 6 and 7 and directing nozzle 14 into conduit 16. Other maneuvering of the vessel, such as turning, can be performed in a variety of manners which might include simply the shutting-off of one or the other of conduits 6 or 7. Also, if it should be considered desirable, an additional nozzle can be provided so as to permit the application of a braking force through either conduit 16 or 17 at the time that the aft discharge is being limited to one or the other of conduit 6 or 7. As with discharge conduits 6 and 7, the particular size or inclination of conduits 16 and 17 must depend upon prevailing conditions and, to some extent, the size of these conduits affects the dimensions of the venturi.

As to operation, the present hydraulic circuit already has been fully considered both in regards to its flow pattern, its efiiciency and the possibility of maneuvering the ship. Further advantages, such as the simplicity of remote control, convenient access to functional parts, and others should be quite apparent. Briefly reviewed, however, the principal advantage resides in providing a practical method and apparatus for hydraulically propelling a vessel by means of a high volume, low pressure water displacement principle. Although such a propulsion principle is not in itself novel, it is believed that the present circuit for the first time harnesses this principle for practical use. The practicality, of course, is due to the fact that the only power required of the pump is that necessary for driving a limited amount of water through the venturi tube. In such experiments as have been conducted, it has become quite clear that approximately 60% of the total volume of the displacement water can be admitted through either conduit 16 or 17 and, obviously, such an intake limits the capacity of the pump to that required for moving only 40% of the volume. In ship design, this reduced pump capacity is a very substantial advantage not only because of the reduction of power requirements, but also in view of the increased cargo capacity. Further, it will be recognized that a practical hydraulic propulsion of this type is far superior to a propeller drive, one of the less obvious considerations in this regard being that the hydraulic propulsion is capable of operating at maximum efiiciency at all speeds, While propellers usually maintain a maximum efficiency at one speed and must be supplemented by variable speed machinery to maintain efiiciency within a comparatively short range of speeds. Further, it will be appreciated that hydraulic propulsion has the characteristic of being relatively noiseless and free from vibrations, which, particularly in modern warfare, has become a very substantial consideration. The more obvious benefits de-' rived from a practical hydraulic propulsion include the elimination of the propeller shafts and their associated drives, the elimination of steering engines, reduction gears and reversing turbines, as well as the increase in mechauical etfieiency and the advantages of maneuverability due to the fact that steerage can be maintained even though the speed of the ship is near zero.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

I claim:

Hydraulic propulsion apparatus for marine ships, said apparatus including a discharge conduit provided with an aft discharge port, at least two water intake conduits both opening externally of the ship, and a pump connected on its suction side to only one of said intake conduits and on its pressure side to said discharge conduit, said discharge conduit discharging aft and being formed with a reduced neck portion and an outwardly diverging portion extending from said neck to said aft discharge port for forming a venturi, said pump being adapted to direct its intake through said reduced neck portion toward said discharge port whereupon an intake suction pressure is created near said venturi neck, and said remaining intake conduit being in communication with said venturi neck concurrently with said pump suction-connected intake for permitting said venturi suction to draw in such an additional volume of water as is needed for ship propulsion, said additional volume being drawn in wholly in response to the reduced pressure created at said venturi neck by said pump.

References Cited in the file of this patent UNITED STATES PATENTS 550,244 Blagburn Nov. 26, 1895 1,259,753 Lassell Mar. 19, 1918 1,721,827 Mauquoi July 23, 1929 FOREIGN PATENTS 414,497 France Sept. 3, 1910 

